There is a bug in the way certain RCA codes have been programmed, so every second command doesn't work. Have you found that only certain number buttons work?
If all your number buttons work then it may well be that you have to reprogram the malfunctioning buttons with advanced codes.
Here's a test you can do. Cover the IR window of the C6 with your hand, then press the channel up button. Keeping the channel up button pressed, now uncover the IR window and point the C6 at the DSS, does the channel up work now?
There is a bad code at the beginning of the signal.
Rob.
http://www.hifi-remote.com/